1. Field of the Invention
The present invention relates to a rolling guide unit that guides an object to be moved, and which is equipped on, for example, a machine tool or industrial robot.
2. Description of the Prior Art
An example of this type of rolling guide unit of the prior art is the rolling guide unit shown in FIGS. 1 and 2.
As shown in the drawings, said rolling guide unit has track rail 1, in which tracks in the form of a pair of track grooves 1a are formed in both the right and left sides along the lengthwise direction, a slider in the form of sliding unit 3 having rolling element circulating path 2 (to be later described in detail) and able to move relative to said track rail 1, and a plurality of rolling elements in the form of balls 4, that bear the load between track rail 1 and sliding unit 3 by circulating while rolling over the above-mentioned track grooves 1a accompanying movement of sliding unit 3, and which are arranged and contained within said rolling element circulating path 2.
Sliding unit 3 has casing 6, provided so as to stride over track rail 1, a pair of end caps 7a and 7b coupled to both front and back ends of said casing 6, and two seals 8a and 8b attached on each of the outer surfaces of said end caps 7a and 7b. Furthermore, grease nipple 9 is attached to end cap 7a for supplying grease to the above-mentioned balls 4. As shown in FIG. 2, rolling element circulating path 2 is composed of load bearing track groove 2a, namely a load bearing track, and return path 2b, formed linearly and in parallel with each other in casing 6, and a pair of roughly semicircular direction changing paths 2c and 2d formed in both end caps 7a and 7b that connect said loading bearing track groove 2a and return path 2b at both their ends. Furthermore, the above-mentioned load bearing track groove 2a corresponds to track groove 1a of track rail 1. In addition, in FIG. 1, reference numerals 11 and 12 indicate retaining members that prevent balls 4 from falling out of the above-mentioned load bearing track groove 2a when sliding unit 3 is removed from track rail 1.
The rolling guide unit having the above-mentioned constitution is arranged on, for example, the bed of a machine tool (not shown), and track rail 1 is fastened to said bed with bolts (not shown). A table for holding a workpiece and so forth (not shown) is bolted to sliding unit 3, and this operates in the form of the moving side. Namely, said table is moved back and forth by a driving device (not shown) with a workpiece and so forth placed on top of said table. Furthermore, as shown in FIG. 1, a plurality of bolt insertion holes 1b are formed in track rail 1 in which bolts are inserted for fastening to the above-mentioned bed and so forth. In addition, a plurality of threaded holes 6a are formed in the upper surface of casing 6 of sliding unit 3. The above-mentioned table is fastened to sliding unit 3 by bolts (not shown) screwed into these threaded holes 6a.
In the rolling guide unit described above, although sliding unit 3 moves smoothly as a result of balls 4 rolling over track groove 1a while circulating within rolling element circulating path 2, this constitution has the disadvantage of the movement of balls 4 producing noise and vibrations. Particularly when balls 4 move into load bearing track groove 2a from direction changing path 2c or 2d of rolling element circulating path 2, said balls 4 collide with the track surface of track groove 1a. Conversely, when balls 4 move from said load bearing track groove 2a into direction changing path 2c or 2d, said balls 4 collide with the inside wall surfaces of the connecting portions of said load bearing track groove 2a and direction changing path 2c or 2d, thus causing the production of relatively large levels of noise and vibration.